Sort objects before relocations

ChangeLog

@@ -1,3 +1,14 @@
+2012-01-27  Ulrich Drepper  <drepper@gmail.com>
+
+	[BZ #13618]
+	* elf/dl-open.c (dl_open_worker): Sort objects by dependency before
+	relocation.
+	* Makeconfig (libm): Define.
+	* elf/Makefile: Add rules to build and run tst-relsort1.
+	* elf/tst-relsort1.c: New file.
+	* elf/tst-relsort1mod1.c: New file.
+	* elf/tst-relsort1mod2.c: New file.
+
 2012-01-26  Joseph Myers  <joseph@codesourcery.com>
 
 	* crypt/md5.h: Remove __STDC__ conditionals.

Makeconfig

@@ -900,6 +900,12 @@ else
 libdl = $(common-objpfx)dlfcn/libdl.a
 endif
 
+ifeq ($(build-shared),yes)
+libm = $(common-objpfx)math/libm.so$(libm.so-version)
+else
+libm = $(common-objpfx)math/libm.a
+endif
+
 # These are the subdirectories containing the library source.  The order
 # is more or less arbitrary.  The sorting step will take care of the
 # dependencies.

NEWS

@@ -1,4 +1,4 @@
-GNU C Library NEWS -- history of user-visible changes.  2012-1-26
+GNU C Library NEWS -- history of user-visible changes.  2012-1-27
 Copyright (C) 1992-2009, 2010, 2011, 2012 Free Software Foundation, Inc.
 See the end for copying conditions.
 
@@ -10,7 +10,7 @@ Version 2.16
 * The following bugs are resolved with this release:
 
   13525, 13526, 13527, 13528, 13529, 13531, 13532, 13533, 13547, 13530,
-  13551, 13552, 13553, 13555, 13559, 13583
+  13551, 13552, 13553, 13555, 13559, 13583, 13618
 
 * ISO C11 support:
 

elf/Makefile

@@ -124,7 +124,8 @@ distribute	:= rtld-Rules \
 		   tst-initordera1.c tst-initordera2.c tst-initorderb1.c \
 		   tst-initorderb2.c tst-initordera3.c tst-initordera4.c \
 		   tst-initorder.c \
-		   tst-initorder2.c
+		   tst-initorder2.c \
+		   tst-relsort1.c tst-relsort1mod1.c tst-relsort1mod2.c
 
 CFLAGS-dl-runtime.c = -fexceptions -fasynchronous-unwind-tables
 CFLAGS-dl-lookup.c = -fexceptions -fasynchronous-unwind-tables
@@ -227,7 +228,7 @@ tests += loadtest restest1 preloadtest loadfail multiload origtest resolvfail \
 	 tst-audit1 tst-audit2 \
 	 tst-stackguard1 tst-addr1 tst-thrlock \
 	 tst-unique1 tst-unique2 tst-unique3 tst-unique4 \
-	 tst-initorder tst-initorder2
+	 tst-initorder tst-initorder2 tst-relsort1
 #	 reldep9
 test-srcs = tst-pathopt
 selinux-enabled := $(shell cat /selinux/enforce 2> /dev/null)
@@ -290,7 +291,9 @@ modules-names = testobj1 testobj2 testobj3 testobj4 testobj5 testobj6 \
 		tst-initordera1 tst-initorderb1 \
 		tst-initordera2 tst-initorderb2 \
 		tst-initordera3 tst-initordera4 \
-		tst-initorder2a tst-initorder2b tst-initorder2c tst-initorder2d
+		tst-initorder2a tst-initorder2b tst-initorder2c \
+		tst-initorder2d \
+		tst-relsort1mod1 tst-relsort1mod2
 ifeq (yes,$(have-initfini-array))
 modules-names += tst-array2dep tst-array5dep
 endif
@@ -1195,3 +1198,9 @@ CFLAGS-tst-auditmod6b.c += $(AVX-CFLAGS)
 CFLAGS-tst-auditmod6c.c += $(AVX-CFLAGS)
 CFLAGS-tst-auditmod7b.c += $(AVX-CFLAGS)
 endif
+
+$(objpfx)tst-relsort1: $(libdl)
+$(objpfx)tst-relsort1mod1.so: $(libm) $(objpfx)tst-relsort1mod2.so
+$(objpfx)tst-relsort1mod2.so: $(libm)
+$(objpfx)tst-relsort1.out: $(objpfx)tst-relsort1mod1.so \
+			   $(objpfx)tst-relsort1mod2.so

elf/dl-open.c

@@ -1,5 +1,5 @@
 /* Load a shared object at runtime, relocate it, and run its initializer.
-   Copyright (C) 1996-2007, 2009, 2010, 2011 Free Software Foundation, Inc.
+   Copyright (C) 1996-2007, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -302,45 +302,109 @@ dl_open_worker (void *a)
   if (GLRO(dl_lazy))
     reloc_mode |= mode & RTLD_LAZY;
 
-  /* Relocate the objects loaded.  We do this in reverse order so that copy
+  /* Sort the objects by dependency for the relocation process.  This
-     relocs of earlier objects overwrite the data written by later objects.  */
+     allows IFUNC relocations to work and it also means copy
-
+     relocation of dependencies are if necessary overwritten.  */
+  size_t nmaps = 0;
   struct link_map *l = new;
-  while (l->l_next)
+  do
-    l = l->l_next;
-  while (1)
     {
       if (! l->l_real->l_relocated)
+	++nmaps;
+      l = l->l_next;
+    }
+  while (l != NULL);
+  struct link_map *maps[nmaps];
+  nmaps = 0;
+  l = new;
+  do
+    {
+      if (! l->l_real->l_relocated)
+	maps[nmaps++] = l;
+      l = l->l_next;
+    }
+  while (l != NULL);
+  if (nmaps > 1)
+    {
+      char seen[nmaps];
+      memset (seen, '\0', nmaps);
+      size_t i = 0;
+      while (1)
 	{
-#ifdef SHARED
+	  ++seen[i];
-	  if (__builtin_expect (GLRO(dl_profile) != NULL, 0))
+	  struct link_map *thisp = maps[i];
+
+	  /* Find the last object in the list for which the current one is
+	     a dependency and move the current object behind the object
+	     with the dependency.  */
+	  size_t k = nmaps - 1;
+	  while (k > i)
 	    {
-	      /* If this here is the shared object which we want to profile
+	      struct link_map **runp = maps[k]->l_initfini;
-		 make sure the profile is started.  We can find out whether
+	      if (runp != NULL)
-		 this is necessary or not by observing the `_dl_profile_map'
+		/* Look through the dependencies of the object.  */
-		 variable.  If was NULL but is not NULL afterwars we must
+		while (*runp != NULL)
-		 start the profiling.  */
+		  if (__builtin_expect (*runp++ == thisp, 0))
-	      struct link_map *old_profile_map = GL(dl_profile_map);
+		    {
+		      /* Move the current object to the back past the last
+			 object with it as the dependency.  */
+		      memmove (&maps[i], &maps[i + 1],
+			       (k - i) * sizeof (maps[0]));
+		      maps[k] = thisp;
 
-	      _dl_relocate_object (l, l->l_scope, reloc_mode | RTLD_LAZY, 1);
+		      if (seen[i + 1] > 1)
+			{
+			  ++i;
+			  goto next_clear;
+			}
 
-	      if (old_profile_map == NULL && GL(dl_profile_map) != NULL)
+		      char this_seen = seen[i];
-		{
+		      memmove (&seen[i], &seen[i + 1],
-		  /* We must prepare the profiling.  */
+			       (k - i) * sizeof (seen[0]));
-		  _dl_start_profile ();
+		      seen[k] = this_seen;
 
-		  /* Prevent unloading the object.  */
+		      goto next;
-		  GL(dl_profile_map)->l_flags_1 |= DF_1_NODELETE;
+		    }
-		}
+
+	      --k;
 	    }
-	  else
-#endif
-	    _dl_relocate_object (l, l->l_scope, reloc_mode, 0);
-	}
 
-      if (l == new)
+	  if (++i == nmaps)
-	break;
+	    break;
-      l = l->l_prev;
+	next_clear:
+	  memset (&seen[i], 0, (nmaps - i) * sizeof (seen[0]));
+	next:;
+	}
+    }
+
+  for (size_t i = nmaps; i-- > 0; )
+    {
+      l = maps[i];
+
+#ifdef SHARED
+      if (__builtin_expect (GLRO(dl_profile) != NULL, 0))
+	{
+	  /* If this here is the shared object which we want to profile
+	     make sure the profile is started.  We can find out whether
+	     this is necessary or not by observing the `_dl_profile_map'
+	     variable.  If it was NULL but is not NULL afterwars we must
+	     start the profiling.  */
+	  struct link_map *old_profile_map = GL(dl_profile_map);
+
+	  _dl_relocate_object (l, l->l_scope, reloc_mode | RTLD_LAZY, 1);
+
+	  if (old_profile_map == NULL && GL(dl_profile_map) != NULL)
+	    {
+	      /* We must prepare the profiling.  */
+	      _dl_start_profile ();
+
+	      /* Prevent unloading the object.  */
+	      GL(dl_profile_map)->l_flags_1 |= DF_1_NODELETE;
+	    }
+	}
+      else
+#endif
+	_dl_relocate_object (l, l->l_scope, reloc_mode, 0);
     }
 
   /* If the file is not loaded now as a dependency, add the search

elf/tst-relsort1.c

@@ -0,0 +1,19 @@
+#include <dlfcn.h>
+#include <stdio.h>
+
+
+static int
+do_test ()
+{
+  const char lib[] = "$ORIGIN/tst-relsort1mod1.so";
+  void *h = dlopen (lib, RTLD_NOW);
+  if (h == NULL)
+    {
+      puts (dlerror ());
+      return 1;
+    }
+  return 0;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"

elf/tst-relsort1mod1.c

@@ -0,0 +1,7 @@
+extern int foo (double);
+
+int
+bar (void)
+{
+  return foo (1.2);
+}

elf/tst-relsort1mod2.c

@@ -0,0 +1,7 @@
+#include <math.h>
+
+int
+foo (double d)
+{
+  return floor (d) != 0.0;
+}